M.Ing. / Vehicles used in military, agricultural, forestry, or construction applications often encounter different road surfaces during a single journey. In order to optimise the mobility of these vehicles, different tyre pressures are required for different types of terrain (sand, mud, cross country, tar road, etc.). An in-motion tyre pressure control system will enable the vehicle's operator to change the tyre pressures without leaving the vehicle. Such a system will not only allow optimum surface contact between the tyres and the terrain - thus improving vehicletraction, but it can also increase the lifespan of the tyres and reduce fuel consumption. The key design criteria for such a system are: quick reaction times, an effective operator interface, and reliability. In case of system failure, the operator must be able to override the control, and the tyres should be inflated to a pre-set default pressure. When the fault had been corrected, the system can be restarted from within the cabin, to inflate or deflate the tyres as required. The focus of this thesis is on the design criteria of a tyre pressure control system, receiving inputs from the driver and from onboard vehicle sensors; and then adjusting individual tyre pressures if necessary, while the vehicle is on the move. Based on the inputs to the control system, the optimum setting for the tyre pressure is determined from a look-up table stored in memory of an onboard computer. This table contains the pressure-speed and pressure-axle load relationship. A unique relation is programmed into the microprocessor for each different vehicle. To install a tyre pressure control system on a vehicle, a computer program is used to control the following hardware which are necessary to inflate or deflate tyres: An air compressor and storage tank. Pneumatic valve. Rotating seal. Pressure and speed sensing elements. Electronic control unit. An experimental set-up was built, from various components or sub-systems, which were integrated systematically until the system was working as a unit. The functionality of the system was tested, and although the results obtained do not yet justify the commercial manufacturing of such systems, it is trusted that this research has contributed towards the increased emphasis that is placed upon vehicle safety and comfort systems.

Not available / text

Made available in DSpace on 2014-06-11T19:24:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-01-30Bitstream added on 2014-06-13T20:32:00Z : No. of bitstreams: 1 mazetto_fr_me_botfca.pdf: 1022011 bytes, checksum: 265f29fb21da2dc260b7ff72711bd637 (MD5) / Universidade Estadual Paulista (UNESP) / O desempenho operacional dos tratores agrícolas é dependente da interação dos rodados e a superfície de contato, sendo de extrema importância a seleção do tipo de pneu, pressão de inflação e lastragem para as diversas operações agrícolas, proporcionando maior eficiência de tração e menor compactação do solo, racionalizando assim, os custos operacionais do sistema produtivo. O presente trabalho teve como objetivo avaliar e correlacionar as metodologias de determinação das áreas de contato e deformações elásticas de pneus agrícolas em superfícies rígida e deformável, em função das pressões de inflação e das cargas radiais, com a finalidade de identificar a metodologia mais acurada e prática para cada condição de ensaio estático de pneus. O experimento foi realizado no Núcleo de Ensaio de Máquinas e Pneus Agrícolas (NEMPA) da Faculdade de Ciências Agronômicas - UNESP, Câmpus de Botucatu, SP. Os pneus estudados foram do tipo R1 com as seguintes dimensões: pneu baixa pressão e alta flutuação (500/60-26.5) inflado com as pressões de 206,7 kPa, 103,3 kPa e 68,9 kPa; radial (14.9R26) com pressões de inflação de 186,1 kPa, 137,8 kPa e 68,9 kPa e diagonal (14.9-26) com pressões de 206,7 kPa, 137,8 kPa e 68,9 kPa; submetidos as cargas de 5 kN, 10 kN, 15 kN e 20 kN aplicadas por uma prensa hidráulica. As áreas de contato dos pneus agrícolas em superfície deformável foram obtidas em tanque de solo e em superfície rígida pelo método do pó, carbono e massa. Os valores das áreas de contato foram determinados por duas metodologias de cálculo: equação da elipse e digitalização das áreas. Os resultados permitiram concluir que a metodologia de cálculo das áreas de contato através da equação da elipse é confiável e prática para obter as áreas de contato dos pneus agrícolas... / The agricultural tractor performance is depended of interaction among the tire and contact surface, and then, the selection of tire type, its inflation pressure and tractor ballast are very important to several conditions of agricultural operation, proportioning higher efficiency of machines and lower soil compaction, rationalizing the operations costs of crop systems. This present research had for main objective the evaluation and correlation of methodologies of tire/ground contact areas and elastic deformations of agricultural tires on rigid and deformable surfaces, in function of inflation pressures and ballasts, identifying the methodology most accuracy and practice for each condition of tire static test. The research was carried out at Agricultural Machinery and Tire Testing Center (NEMPA), Rural Engineering Department of Agronomic Science College, Sao Paulo State University (UNESP), Botucatu/SP, Brazil. The studied tires were of R1 type with the following dimensions: low pressure and high fluctuation tire (500/60-26.5) inflated with pressures of 206,7 kPa, 103,3 kPa and 68,9 kPa; radial ply (14.9R26) with inflation pressures of 186,1 kPa, 137,8 kPa and 68,9 kPa and bias ply (14.9-26) with pressures of 206,7 kPa, 137,8 kPa and 68,9 kPa. Four ballast conditions were applied on the wheels by hydraulic press: 5 kN, 10 kN, 15 kN and 20 kN. The contact areas of the agricultural tires on deformable surface were obtained in soil bin and on rigid surface by powder, carbon paper and modelling mass methods. The contact area values were determined by two calculus methodologies: ellipse equation and areas digitalization. The results of methodologies used to calculate the contact areas permit to conclude that ellipse equation can estimate with precision and practice the contact areas of agricultural tires...

Resumo: O desempenho operacional dos tratores agrícolas é dependente da interação dos rodados e a superfície de contato, sendo de extrema importância a seleção do tipo de pneu, pressão de inflação e lastragem para as diversas operações agrícolas, proporcionando maior eficiência de tração e menor compactação do solo, racionalizando assim, os custos operacionais do sistema produtivo. O presente trabalho teve como objetivo avaliar e correlacionar as metodologias de determinação das áreas de contato e deformações elásticas de pneus agrícolas em superfícies rígida e deformável, em função das pressões de inflação e das cargas radiais, com a finalidade de identificar a metodologia mais acurada e prática para cada condição de ensaio estático de pneus. O experimento foi realizado no Núcleo de Ensaio de Máquinas e Pneus Agrícolas (NEMPA) da Faculdade de Ciências Agronômicas - UNESP, Câmpus de Botucatu, SP. Os pneus estudados foram do tipo R1 com as seguintes dimensões: pneu baixa pressão e alta flutuação (500/60-26.5) inflado com as pressões de 206,7 kPa, 103,3 kPa e 68,9 kPa; radial (14.9R26) com pressões de inflação de 186,1 kPa, 137,8 kPa e 68,9 kPa e diagonal (14.9-26) com pressões de 206,7 kPa, 137,8 kPa e 68,9 kPa; submetidos as cargas de 5 kN, 10 kN, 15 kN e 20 kN aplicadas por uma prensa hidráulica. As áreas de contato dos pneus agrícolas em superfície deformável foram obtidas em tanque de solo e em superfície rígida pelo método do pó, carbono e massa. Os valores das áreas de contato foram determinados por duas metodologias de cálculo: equação da elipse e digitalização das áreas. Os resultados permitiram concluir que a metodologia de cálculo das áreas de contato através da equação da elipse é confiável e prática para obter as áreas de contato dos pneus agrícolas... / Abstract: The agricultural tractor performance is depended of interaction among the tire and contact surface, and then, the selection of tire type, its inflation pressure and tractor ballast are very important to several conditions of agricultural operation, proportioning higher efficiency of machines and lower soil compaction, rationalizing the operations costs of crop systems. This present research had for main objective the evaluation and correlation of methodologies of tire/ground contact areas and elastic deformations of agricultural tires on rigid and deformable surfaces, in function of inflation pressures and ballasts, identifying the methodology most accuracy and practice for each condition of tire static test. The research was carried out at Agricultural Machinery and Tire Testing Center (NEMPA), Rural Engineering Department of Agronomic Science College, Sao Paulo State University (UNESP), Botucatu/SP, Brazil. The studied tires were of R1 type with the following dimensions: low pressure and high fluctuation tire (500/60-26.5) inflated with pressures of 206,7 kPa, 103,3 kPa and 68,9 kPa; radial ply (14.9R26) with inflation pressures of 186,1 kPa, 137,8 kPa and 68,9 kPa and bias ply (14.9-26) with pressures of 206,7 kPa, 137,8 kPa and 68,9 kPa. Four ballast conditions were applied on the wheels by hydraulic press: 5 kN, 10 kN, 15 kN and 20 kN. The contact areas of the agricultural tires on deformable surface were obtained in soil bin and on rigid surface by powder, carbon paper and modelling mass methods. The contact area values were determined by two calculus methodologies: ellipse equation and areas digitalization. The results of methodologies used to calculate the contact areas permit to conclude that ellipse equation can estimate with precision and practice the contact areas of agricultural tires... / Orientador: Kléber Pereira Lanças / Coorientador: Reginaldo Barboza da Silva / Banca: Afonso Lopes / Banca: Marcos Milan / Mestre

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A major problem of agricultural tractor during several operations in which it is used is the difficulty of working in various moisture conditions and soil types affect your ability to traction force, slip and fuel consumption. What has been observed is that with increased contact surface between the tire of the tractor and the ground, there is the possibility of reductions in slippage, since it compensates with its increased weight on the wheels. Considering the importance of agricultural tractors and characteristics of pneumatic tires to develop traction force and the fluctuation in the soil, this study aimed at comparing the use of single and dual tires on the rear axle of a tractor equipped with front wheel assist (FWA ) with different tire inflation pressures internal to the tractor and shot at a fixed pressure of the external configuration of dual tires, to assess performance in traction, using as parameters to assess the strength available: the drawbar pull, fuel consumption, the slip. Were also assessed indirectly by the pressure applied by the treads to the ground, weight transfer, forward kinematics, drawbar power, traction efficiency, dynamic coefficient of traction. It was found that the use of dual tires increases the contact surface of the tire with the soil may reach 13% increase from the surface, there are increments of 4.35% in the traction force on the use of dual tires in relation to the single increases in 7.5% of the available power at the drawbar when used double wheels at a pressure of 138 kPa. There was no difference in the slip to both axles. It was also found that the use of dual tires led to the highest efficiency in the drawbar that for the single, with the highest efficiency of 72.8%. The treatment produced the best results in this analysis was to run the setup dual tires with the pressure of 138 kPa. / Um dos maiores problemas do trator agrícola durante as diversas operações em que ele é utilizado é a dificuldade de se trabalhar nas mais diversas condições de umidade e tipos de solo afetando a sua capacidade de força de tração, consumo de combustível e patinamento. O que se tem observado é que, com o aumento da superfície de contato entre o pneu do trator agrícola e o solo, há a possibilidade de reduções dos índices de patinamento, desde que se compense com o respectivo aumento de peso sobre os rodados. Considerando a importância dos tratores agrícolas e características dos seus rodados pneumáticos em desenvolver força de tração e flutuação no solo, o presente trabalho analisou comparativamente o uso de rodado simples e rodado duplo no eixo traseiro de um trator agrícola dotado de tração dianteira auxiliar (TDA), com diferentes pressões de insuflagem dos pneus internos do trator e a uma pressão fixa no rodado externo da configuração de rodado duplo, para avaliação de desempenho em tração, utilizando-se como parâmetros de avaliação: a força disponível na barra tração, o consumo de combustível e o patinamento. Também foram avaliados indiretamente a pressão aplicada ao solo pelos rodados, transferência de peso, avanço cinemático, potência disponível na barra de tração, eficiência em tração, coeficiente dinâmico de tração. Foi verificado que o uso de rodado duplo aumenta a superfície de contato do pneu com o solo podendo chegar a 13 % de aumento dessa superfície, há incrementos da ordem de 4,35 % na força de tração na utilização de rodado duplo em relação ao rodado simples, aumenta-se em 7,5 % a potência disponível na barra de tração quando utilizado rodado duplo na pressão de 138 kPa. Não houve diferença no patinamento para ambos os rodados. Verificou-se também que a utilização de rodado duplo proporcionou maiores valores de eficiência em tração que para o rodado simples, sendo a maior eficiência de 72,8%. O tratamento que apresentou os melhores resultados nesta análise foi para a configuração rodado duplo na pressão de 138 kPa.

No description available.

The ability of vehicles to traverse soft soils is an important aspect of their performance. The geological, climate and topography diversity originated, in Rio Grande do Sul, extensive areas of hydromorphic clay soils, as example, Planssoils and Gleissoils. When saturated of water, these soft soils present low loads support, difficult agricultural machinery work and limit the traverse of military wheeled vehicles. The aim of this study was to determine the limit of soil conditions for trafficability of military 6 x 6 wheeled trucks (Cascavel and Urutu), determine the ground pressure and predict the mobility condition from soil cone index (SCI) and vehicle characteristics. This study also proposed to evaluate the performance of a four wheel drive tractor in drawbar pull test and trafficability performance, to correlate the reduced tire inflation pressure and vehicle loading effect on slipping, drawbar pull, fuel consumption and mobility under different soil moisture conditions. It was found that the Cascavel military truck had a minimal ground pressure of 357 kPa and it needed SCI of 402 kPa in the critical layer for a single pass. The Urutu truck had a ground pressure of 401 kPa and required at least 431 kPa in SCI for one-way pass. The NATO Reference Mobility Model (NRMM) and Mean Maximum Pressure (MPP) predicting model underestimate the soil cone index required for these military vehicles to traverse soft-soils, however, MMP was more appropriate to predict the correct SIC for the tested vehicles. For the tractor experiment it was found that tire inflation pressure changed the ground pressure and the vehicle loading didn t change the ground surface pressure. The greatest drawbar pull were obtained at low tractor speed, reduced inflation pressure and high loading level, operating on hard ground. The lowest specific fuel consumption was obtained on hard ground, empty weight, low tire pressure and operating in high speed gear. The increase of soil moisture decreased the dynamic traction coefficient from 0.57 to 0.31 and the traction efficiency decrease from 50 to 37%. Reduced inflation tire pressure had positive effects on tractor mobility in waterlogged soils, reducing slipping and increasing traverse speed. Using height loading level had negative effect on wet soils because it require more engine power and increase the fuel consumption. / A habilidade de um veículo se locomover em solos com baixa capacidade de carga é um aspecto importante em seu desempenho. A diversidade geológica, climática e de relevo originou, no Rio Grande do Sul, extensas áreas de solos Hidromórficos argilosos, entre eles, os Planossolos e os Gleissolos. Quando saturados, estes solos apresentam baixa capacidade de suporte de carga, dificultando o trabalho de máquinas agrícolas e o deslocamento de veículos militares de roda. O presente trabalho teve por objetivo determinar as condições de solo limite para a trafegabilidade de veículos militares de roda com tração 6 x 6 (Cascavel e Urutu), determinar a pressão de contato pneu-solo e predizer a condição de mobilidade a partir índice de cone do solo (ICS) e das características do veículo. O trabalho também propôs avaliar o desempenho de um trator agrícola com TDA em ensaio de tração e trafegabilidade, para verificar a influência da baixa pressão interna dos pneus e a quantidade de lastro do trator sobre o patinamento dos rodados, a capacidade de tração, o consumo de combustível e a mobilidade sob diferentes condições de umidade do solo. Foi verificado que a viatura militar Cascavel exerce pressão mínima pneu-solo de 357 kPa e requer ICS de 402 kPa na camada crítica para se locomover. O veículo Urutu exerce uma pressão pneu-solo de 401 kPa e necessita de uma resistência do solo mínima de 431 kPa para o tráfego singular. Os modelos de predição de trafegabilidade de veículos militares NATO Reference Mobility Model (NRMM) e Mean Maximum Pressure (MMP) subestimam o ICS necessário para os solos estudados, porém, o modelo que mais aproximou o ICS ao requerido pelos veículos testados foi o MMP. No experimento com tratores verificou-se que a pressão interna dos pneus alterou e a adição de lastro não alterou a superfície de contato pneu-solo. Os maiores esforços na barra de tração foram obtidos em baixa velocidade de deslocamento, baixa pressão interna dos pneus e com trator completamente lastrado, operando em solo firme. O menor consumo específico de combustível foi obtido em solo firme, com trator sem lastro, baixa pressão nos pneus e operando em marcha alta. O acréscimo de umidade no solo diminuiu o coeficiente dinâmico de tração de 0,57 para 0,31 e a eficiência de tração de 50 para 37%. A utilização de baixa pressão interna nos pneus tem efeitos positivos na trafegabilidade em solos alagados, reduzindo significativamente o patinamento e aumentando a velocidade de deslocamento. A utilização de lastro no trator em condições de solo saturado tem efeito negativo, porque aumenta a demanda de potência e o consumo de combustível da operação.

L’objectif principal de cette thèse est de modéliser en flambement des poutres pressurisées en tissu souple homogène orthotrope (THO) composite. La première partie détaille les études expérimentales qui ont été menées sur des poutres gonflables à certain niveaux de pression afin de caractériser les propriétés mécaniques du matériau et le comportement en flambement de la structure. Dans une deuxième partie, une approche analytique a été envisagée afin d’étudier le flambement ainsi que le comportement d’une poutre gonflable orthotrope. Un modèle 3D gonflables poutre orthotrope basé sur la cinématique de Timoshenko a été présenté brièvement. La charge critique a été étudiée pour différents cas de charge avec différentes conditions aux limites. Les résultats ont été confrontés aux résultats théoriques disponibles. Pour vérifier la limite de validité des résultats, la charge d’apparition des plis a également fait l’objet d’une étude pour chacun des cas. La dernière partie est consacrée à une étude linéaire et à une analyse non-linéaire du flambement de la poutre gonflable en THO composite. Le modèle éléments finis (MEF) établi ici implique un élément poutre de Timoshenko à trois-nœuds avec une continuité de type C0. Un test de convergence du maillage sur la force critique de la poutre a été réalisé par la résolution du problème aux valeurs propres. En outre, un MEF non-linéaire a été développé en utilisant la procédure itérative de quasi-Newton avec incréments de chargement adaptatif permettant le tracé pas à pas de la réponse charge-déflexion de la poutre. Les résultats ont été validés à partir d’un certain niveau de pression par des résultats expérimentaux et numériques / The main goals of this thesis are to modeling and to perform the buckling study of inflatable beams made from homogeneous orthotropic woven fabric (HOWF) composite. Three main scenarios were investigated in this thesis. The first is the experimental studies which were performed on HOWF inflatable beam in various inflation pressures for characterizing the orthotropic mechanical properties and buckling behaviors of the beam. In the second scenario, an analytical approach was considered to study the buckling and the behavior of an inflatable orthotropic beam. A 3D inflatable orthotropic beam model based on the Timoshenko's kinematics was briefly introduced: the nonlinearities (finite rotation, follower forces) were included in this model. The results were compared with theoretical results available in the literature. To check the limit of validity of the results, the wrinkling load was also presented in every case. The last scenario is devoted to the linear eigen and non-linear buckling analysis of inflatable beam made of HOWF. The finite element (FE) model established here involves a three-noded Timoshenko beam element with C0-type continuity for the transverse displacement and quadratic shape functions for the bending rotation and the axial displacement. In the linear buckling analysis, a mesh convergence test on the beam critical load was carried out by solving the linearized eigenvalue problem. In addition, a nonlinear FE model was developed by using the quasi-Newton iteration with adaptive load stepping for tracing load-deflection response of the beam. The results were validated from a certain pressure level by experimental and thin-shell FE results

In this thesis, an effect of a tyre defect on the driving dynamics of a vehicle is dealt with. The first part of the thesis is mainly concerned with the vehicle dynamics, road resistance, adhesion, orientation characteristics of the tyres and slowing down. This chapter is followed by an overview of the manufacturing process and construction of modern passenger car tyres. The practical part is focused on driving tests that are used to demonstrate the influence of tyre defects on handling characteristics of the vehicle. The main focus of this thesis is on directional variation, braking distance, deceleration and lateral acceleration. The very end of the thesis concentrates on tyre defect in higher speeds and its after-effects as well as precautions for mitigation of these after-effects.